/* eslint-disable no-undef */
/* eslint-disable no-unused-vars */
// 1、js一共有多少种数据类型?
//Boolean, String, Number, 对象, 数组, 函数;
// 2、js检测数据类型有哪些方法?
//typeof 数值;
//需要检测数据 instanceof 构造函数;
//Object.prototype.toString.call(需要检测的数据);
// 3、undefined和null的区别?	用typeof检测它们分别返回什么值?
// undefined是未定义, 没有赋值;
// null是空值;
// 分别返回undefind和object;
// 4、写出下列对应结果
let str_4 = '0';
Boolean(str_4); //ture

let str1_4 = ''; //空
Boolean(str1_4); //false

let str2_4 = ' '; //空格
Boolean(str2_4); //true

let unde_4 = undefined; //未定义
Boolean(unde_4); //false

let nu_4 = null;
Boolean(nu_4); //false

let num_4 = 0;
Boolean(num_4); //false

let num1_4 = -10;
Boolean(num1_4); //true

// 5、写出下列对应结果	注意：需要分别使用Number、String、toString去转换数据类型
let str_5 = '0';
Number(str_5); //0
String(str_5); //'0'
toString(str_5); //[object String]
let num_5 = -10;
Number(num_5); //-10
String(num_5); //'-10'
toString(num_5); //[object Number]
let flag_5 = true;
Number(flag_5);
String(flag_5); //true
toString(flag_5); //[object Boolean]
let ud_5 = undefined;
Number(ud_5); //NaN
String(ud_5); //'undefined'
toString(ud_5); //[object Undefined]
let nu_5 = null;
Number(nu_5); //0
String(nu_5); //'null'
toString(nu_5); //[object Undefined]
// 6、检测下面的变量各自的数据类型
let str_6 = ''; //String
let num_6 = '-10'; //String
let num1_6 = 0; //Number
let nu_6 = undefined; //Undefined
let nu1_6 = 'undefined'; //String
let nu2_6 = 'null'; //String
let nu3_6 = null; //Undefined
let obj_6 = '{}'; //String
let obj1_6 = {}; //Object
let sy_6 = Symbol('n'); //Symbol
